In hydraulic or airless paint spraying a pump is utilized to pressurize the paint to a sufficiently high pressure so that the paint is atomized upon release from the nozzle of a spray gun attached to the pump outlet by a high pressure hose. The type of pump preferably used for this purpose is the double acting piston pump because of the piston pump's ability to handle high viscosity paints or coatings easily and the capability of the double acting piston pump to pump fluid on both the upstroke and downstroke of the piston thereby providing a continuous flow of paint to the spray gun. An example of such a pump is described in U.S. Patent Publication No. 20160069344, the disclosure of which is incorporated herein by reference.
Such high pressure paint spray pumps are generally driven by a permanent, magnet direct current (PMDC) brushed, brushless or universal electric motor operating on normal residential or commercial 120 or 240 volt alternating current service. The electric motor and the pump are combined together in a unit wherein the motor drive shaft drives the pump through a reduction gear and crank shaft housed in a gear box of the unit. The unit also includes a control box which houses a power supply for the motor and a microprocessor for controlling operation of the motor. Such an electrically operated paint spray unit includes a number of hear generating elements which, if the heat generated thereby becomes excessive, could result in damage or failure of one or more of the electrical components of the paint spray unit with the consequent interruption or cessation of pump operation.